When Quincy saw the length of the line at the department store's cash register, he predicted he'd have to wait 15 minutes. He actually waited only 10 minutes. What is the percent error for Quincy's prediction?


The **percent error** is calculated using the formula:

\[
\text{Percent Error} = \left| \frac{\text{Actual Value} - \text{Predicted Value}}{\text{Predicted Value}} \right| \times 100\%
\]

### Given:
- **Predicted time** = 15 minutes
- **Actual time** = 10 minutes

### Step 1: Find the absolute difference
\[
| 10 - 15 | = 5
\]

### Step 2: Divide by the predicted value
\[
\frac{5}{15} = \frac{1}{3} \approx 0.3333
\]

### Step 3: Multiply by 100 to get the percentage
\[
0.3333 \times 100 = 33.33\%
\]

### Answer:
The **percent error** in Quincy's prediction is **33.33%**.

Would you like a more detailed breakdown or another example?  

Here are five related questions to explore:  
1. What is the percent error if Quincy's actual wait time was 12 minutes instead of 10?  
2. How is percent error different from percentage increase or decrease?  
3. Why do we use absolute value in the percent error formula?  
4. In what real-life situations is percent error commonly used?  
5. How does percent error affect scientific measurements?  

**Tip:** Percent error is always expressed as a **positive value** unless direction matters in a specific context!

When Quincy saw the length of the line at the department store's cash register, he predicted he'd have to wait 15 minutes. He actually waited only 10 minutes. What is the percent error for Quincy's prediction?

Learn how to calculate percent error with a real-life example: Quincy's predicted wait time of 15 minutes versus an actual wait time of 10 minutes. Discover the step-by-step method to find a percent error of 33.33%, covering key concepts like absolute value and division. Perfect for Grades 6-8!

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